The subject of this research project is the structural molecular biology of RNA processing and of the coupling with transcription. Although RNA processing reactions can be reconstituted in vitro, they occur more efficiently in the cell because they are closely integrated with transcription. How these processes are regulated and integrated with each other remains unclear at the molecular level and even less well understood in structural terms. The specific goal of this proposal is to study how the formation of the mature 3'-end of a messenger RNA by cleavage and polyadenylation is coupled to the termination of transcription and to the subsequent export of the mature RNA from the cell nucleus. In order to address these biological problems, we propose to study: (1) the molecular basis for RNA recognition by RNA processing factors Rna15 and Hrp1, and RNA export factor Npl3, to understand how RNA-binding proteins within the 3'-end processing complex are organized on the processing signals;(2) the interaction of Rna15 with the transcription termination factor Pcf11, to understand how the chain of events leading to transcription termination is initiated once a polydenylation site is transcribed;(3) the molecular basis for the specific recognition of different phosphorylatyed forms of the C- terminal domain of the RNA polymerase by transcription termination factors Rtt103 and Pcf11;(4) how the poly(A) polymerase enzyme responsible for addition of the poly(A) tail is recruited by Fip1 so that the enzyme is only active on pre-mRNAs;(5) the structure of the heterotrimeric protein complex (CstF) that recognizes the 3'-end processing sites of vertebrate mRNAs and couples RNA processing with transcription termination. The integration of gene expression mechanisms adds robustness and allows for multiple levels of regulation. Therefore, dissecting how transcription and RNA processing are coupled at the molecular and structural level, as we propose to do, is an essential step to understanding how gene expression pathways are integrated and regulated.